New Rock Pi 4B+ won't boot

Apologies if I’m posting out of turn as I’m new to Rock Pi (though have a couple of other SBCs). Recently received my new 4B+. I’m finding the board won’t boot. I get a solid green light which my searching of this forum tells me means that it can’t find a boot record - but I thought this came preinstalled with TwisterOS? The HDMI gives me no output at all - I’ve tried multiple cables. I bought my own PD supply as Allnet offered no supply for the UK, I’m guessing this might have something to do with it, but the supply I bought complies with the specification.

Additionally I’m finding when I plug the USB in, it’s random whether the green light comes on or not - and the more I’ve been trying, the more often it doesn’t.

Being new to the Rock I’m not entirely sure what I should be expecting, but I did watch a few youtube videos on it and it seemed to be pretty much plug and play. What am I doing wrong?

Thanks in advance!

I recently bought a Rock Pi 4A+ with 32GB eMMC at Allnet China. I think that the difference between 4 A+ and 4B+ is onboard WiFi/BT chip. The 4A+ does not have the WiFi/BT capabilities. I’m using WiFi and BT USB dongles.
Then, I was able to boot the 4A with the Debian or the Armbian OS from a microSD or an eMMC by following the instructions of I don’t know the ‘preinstalled with TwisterOS’.
I suppose you should refer to the wiki first.
Good luck!

Yup that was it. I was expecting the eMMC to be preinstalled with TwisterOS, as testified by YouTube videos I’d seen. Thanks to the Armbian guys, I was able to sort it out and it’s running just fine now. I’m busy making the tweaks to get it running how I want.